PLC BASED INDUCTION MOTOR STARTING AND PROTECTION

PLC BASED INDUCTION MOTOR STARTING AND PROTECTION

ABSTRACT

The intent of the paper is starting, speed control and protection of induction motor. There by limiting the starting current and increase the starting torque and so as to protect the induction motor. There are different methods for starting of the Slip Ring induction Motor. But we have opted the Rotor Resistance Control method for Starting the Induction Motor. Programming is done by using Programmable Logic Controller; control panel is designed and programmed according to requirements. The motor will start with high rotor resistance and the rotor resistance is cut off with respective time delay and the motor will run at rated speed. The contactor is used for the switching of three phase supply to the stator winding. This is how the starting, speed control and protection of induction motor is achieved and the operation is very reliable, sufficiently high efficient. Induction motors are widely used in many operating areas and industrial applications as they are simple, robust, reliable and have low production costs. The reliability of an induction motor is of great Importance in applications such as commercial, aerospace and military and many industrial applications. In this paper different problems of IM are dealt with as over current, overvoltage, over temperature, over speed, inrush current, vibration monitoring during it’s time of operation. There are various proposed methods for fault diagnosis and protection of IM. Some of them are Stator fault monitoring techniques, protection system using On-line fault detection, Programmable Logic Controller (PLC) based protection system. In this study, the method which is applied is PLC based protection system of an IM.

Keywords— Induction Motor, Rotor resistance, Protection, Speed control, PLC, Ladder logic, Fault diagnosis

INTRODUCTION

The starting, speed control and protection of Induction motor can achieved easily by using PLC. Three-phase induction motors are widely used in industrial drives because they are rugged, reliable and economical. High Starting torque is a desired feature in some special industrial applications which use 3-Ph Slip Ring Induction motor. An induction motor or asynchronous motor is a 3phase 4pole induction motor. This is a type of alternating current motor where power is supplied to the rotor by means of electromagnetic induction. The 3 phase 4pole induction motor electric motor turns because of magnetic force is exert between the stationary electromagnet called the stator and a rotating. The three-phase induction motors are the most widely used electric motors in industry.

They run at essentially constant speed from no-load to full-load. However, the speed is frequency dependent and consequently these motors are not easily adapted to speed control .We usually prefer d.c. motors when large speed variations are required. Nevertheless, the 3-phase induction motors are simple, rugged, low-priced, easy to maintain and can be manufactured with characteristics to suit most industrial requirements.This3phase 4pole inductions electric motor turns because of magnetic force exert between emotion less electromagnet called the stator and a rotating electromagnet called the rotor. If the slip ring induction motor is started with all the slip rings or the rotor terminals shorted, like a normal induction motor, then it suffers extremely high locked rotor current, ranging upto1400%, accompanied with very low locked rotor torque as low as 60%.So,it is not advised to start a slip ring induction motor with its

OVERVIEW OF BLOCK DIAGRAM

 

FIG.1 BLOCK DIAGRAM

PROGRAMMABLELOGIC CONTROLLER

A PLC or a programmable controller is a small computer used for automation of real-world processes, such as control of ma- chinery on factory assembly lines. A PLC can be programmed to sense, activate, and control industrial equipment. Therefore, a PLC incorporates a number of I/O points, which allow electrical signals to be interfaced. Input and output components of the processes are connected to the PLC; and the control program is loaded on the PLC memory. The basic structure of the PLC is illustrated in Fig. 2.

 

FIG2. PROGRAMMABLE LOGIC CONTROLLER

In this study, the PLC measures the current, the voltage, the temperature, and the speed of an induction motor through analog inputs. In addition, it continuously monitors the inputs and activates the outputs according to the program. Siemens PLC S7-200 module with 14 digital input/10 digital output addresses with CPU 224 sample (14∗DI 24 V dc/10∗DO 24 V dc) is preferred due to its easy usefulness in experimental application. The PLC programming memory used is composed of 4096 words. STEP 7—Micro/Win 32 programmer was used as the software. Statement list editor (STL) and ladder diagram (LAD) were used as programming languages. Software of the PLC was prepared on the computer and loaded on the PLC by RS 232-RS 485 PC/planposition indicator (PPI) cable. While the program prepared is being loaded on the PLC from the computer, the most important point is the baud rate between the PLC and the computer. The baud rate must be appropriate to switch setup on the bound cable in manual.

PROTECTION SYSTEM

 

FIG.3.SCHEMATIC DIAGRAM OF THE PROTECTION SYSTEM.

Motor Electrical Protection

• Thermal Overload

• Process Caused (Excessive load)

• High Ambient Conditions (Hot, Blocked Ventilation)

• Power Supply Issues (Voltage/Current Unbalance, Harmonics)

• Phase Fault

• Ground Fault

• Abnormal Operating Conditions

• Over & Under Voltage

• Underfrequency

• Voltage and Current Unbalance

• Load Loss

• Jamming

• Jogging

Overvoltage Protection

The overall result of an overvoltage condition is a decrease in load current and poor power factor. Al though old motors had robust design, new motors are designed close to saturation point for better utilization of core materials and increasing the V/Hz ratio cause saturation of air gap flux leading to motor heating.

The overvoltage element should be set to 110% of the motors nameplate unless otherwise started in the data sheets.

Undervoltage Protection

The overall result of an undervoltage condition is an increase in current and motor heating and a reduction in overall motor performance. The undervoltage protection element can be thought of as backup protection for the thermal overload element. In some cases, if an undervoltage condition exists it may be desirable to trip the motor faster than thermal overload element. The undervoltage rip should be set to 80-90% of nameplate unless otherwise stated on the motor data sheets. Motors that are connected to the same source/bus may experience a temporary undervoltage, when one of motors starts. To override this temporary voltage sags, a time delay set point should be set greater than the motor starting time.

Short Circuit Protection

The short circuit element provides protection for excessively high overcurrent faults Phase-to-phase and phase-to-ground faults are  common types of short circuits When a motor starts, the starting current (which is typically 6 times the Full Load Current) has asymmetrical components . These asymmetrical currents may cause one phase to see as much as 1.7 times the RMS starting current. To avoid nuisance tripping during starting, set the the short circuit protection pick up to a value at least 1.7 times the maximum expected symmetrical starting current of motor. The breaker or contactor must have an interrupting capacity equal to or greater than the maximum available fault current or let an upstream protective device interrupt fault current.

LADDER LOGIC FOR STARTING OF MOTOR DIFFERENT PROGRAMMING LANGUAGES

1. LADDER DIAGRAM

2. FUNCTIONAL BLOCK DIAGRAM LANGUAGE

3. SEQUENTIAL FUNCTION CHART LANGUAGE

4. INSTRUCTION LIST LANGUAGE

HERE WE ARE USED LADDER LOGIC FOR STARTING AND PROTECTION PURPOSE

 

fig.4.ladder logic for starting of motor

CONCLUSION

Speed control and protection of induction motor is achieved and the operation is very reliable, sufficiently high efficient. Without changing in any hardware connection just by simply changing the program in the PLC; the motor can be made to run in for any duration of time. This system also used for one of the starting method of three phase slip ring Induction motor this system not only reduces the starting current to a limit, but also develops High starting torque which is required in many of the induction motor applications. This can be applicable to run the lift, by changing the logic in a program and it can also be used for any industrial applications. This PLC based system requires less hardware compared to any microcontroller or microprocessor based system. Programmable Logic Controllers (PLC) are widely used in industrial control because they are inexpensive, easy to install and very flexible in applications. A PLC interacts with the external world through its inputs and outputs.

REFERENCES:

1. Maria G. Ioannides, “Design And Implementation Of Plc-Based Monitoring Control System For Induction Motor,” Ieee Transactions On Energy Conversion, Vol. 19, No. 3, September 2004.

2. Ravi Masand, DeepikaJadwani, Prof. S.P Shukla, ―Fault Diagnosis Of Induction Motor Using Plc,‖ International Journal Of Advanced Research In Electrical, Electronics And Instrumentation Engineering, Vol. 2, Issue 12, December 2013.

3. Mrs.JigneshaAhir, ―Design And Development Of Plc And Scada Based Control Panel For Continuous Monitoring Of 3- Phase Induction Motor ,‖ National Conference On Recent Trends In Engineering & Technology, May 2011.

4. Colak, H.Celik, ˙i.Sefa, ―On Line Protection System For Induction Motors,‖ Energy Convers. Manage.Vol. 46, No. 17, Pp. 2773–2786, 2005.

5. PROGRAMMABLE LOGIC CONTROLLER, ―AN AUTOMATION TECHNIQUE FOR PROTECTION OF INDUCTION

MOTOR‖ PUBLISH BY INTERNATIONAL RESEARCH JOURNAL OF SUSTAINABLE SCIENCE &ENGG.

6. PLC AND SCADA BASED FAULT DIAGNOSIS OF INDUCTION MOTOR, INTERNATIONAL JOURNAL OF DIGITAL APPLICATION & CONTEMPORARY research (VOLUME 2, ISSUE 6, JANUARY 2014)

7. FAULT DETECTION AND PROTECTION OF INDUCTION MOTORS USING SENSORS-RAMAZANBAYINDIR, MEMBER, IEEE, ˙IBRAHIM SEFA, MEMBER, IEEE, ˙ILHAMICOLAK, MEMBER, IEEE, AND ASKINBEKTAS

8. Y. ZHONGMING AND W. BIN, ―A REVIEW ON INDUCTION MOTOR ONLINE FAULT DIAGNOSIS, IN 3RD INT. POWER ELECTRON. MOTION CONTROL CONF. (PIEMC 2000), VOL. 3, PP. 1353–1358.

9. M. E. H. BENBOUZID, ―BIBLIOGRAPHY ON INDUCTION MOTORS FAULTS DETECTION AND DIAGNOSIS, IEEE TRANS. ENERGY CONVERS., VOL. 14, NO. 4, PP. 1065– 1074, Dec. 1999

10. SIEMENS, S7-200 PROGRAMMABLE CONTROLLER SYSTEM MANUEL, 1999.

11. OKOLI F.I, ONUBOGU J.O, OKEZIE C.C, OKOROGU V.N, ‖THE SIMULATION OF THE CONTROL OF AN INDUSTRIAL MIXER USING PLC’’ INTERNATIONAL JOURNAL OF INVENTIVE ENGINEERING AND SCIENCES (IJIES) ISSN: 2319–9598, VOLUME-1, ISSUE-2, JANUARY 2013, 25.

12. W. T. THOMSON AND M. FENGER, ―CURRENT SIGNATURE ANALYSIS TO DETECT INDUCTION MOTOR FAULTS,‖ IEEE IND. APPL. MAG., VOL. 7, NO. 4, PP. 26–34, JUL./AUG. 2001

IMPLEMENTATION OF PLC BASED ELEVATOR CONTROL SYSTEM

IMPLEMENTATION OF PLC BASED ELEVATOR CONTROL SYSTEM

 Electrical and Electronics Project by Ravi Devani

ABSTRACT

This paper describes programmable logic controller based elevator control system. An elevator is one of the important aspects in electronics control module in automotive application. Nowadays, Myanmar is a developing country and there is enormous increase in high-rise building in Myanmar. This paper mainly focuses on using programmable logic controller to control the circuit and building the elevator model. Hall Effect sensor is used for the elevator position. DC Motor is used to control the up and down movement of the elevator car. Push buttons are used to call the elevator car. The elevator position is described by using the display unit. In this paper, Auto Station Software ladder logic program is used for four floors control system.

Keywords –WPLC, Elevator Design, Hall Effect sensor, DC motor, Ladder logic

INTRODUCTION

For most people residing in urban cities, elevators have become an integral part of their daily life. Simply stated, an elevator is a hoisting or lowering mechanism, designed to carry passengers or freight, and is equipped with a car and platform that typically moves in fixed guides and serves two or more landings. Hydraulic and roped elevators are the two types of elevators in use today. The main design considerations for choosing either electric traction drive or hydraulic for a particular project are the number of floors, the height of the building, the number of people to be transported, desired passenger waiting times and frequency of use.

This project is to design and construct an elevator using a programmable logic controller. Hall Effect sensor is used to know the elevator position. Hydraulic and roped elevators are the two types of elevators in use today. Elevators are prevalent throughout many multi-level structures.

RELATEDWORK

In [9], the author explained that an approximate small-scale elevator model with PLC is adopted for the controller design which uses the Ladder Language based on the GE FANUC Versamax PLC. The ladder logic has implemented by using VersaPro. 2.02. In this control design technique, the Light Dependent Resistor (LDR) is used to sense the elevator floor.GE FANUC Versamax PLC is having a configurable memory of 64kbyte. The author provided to improve the quality in elevator systems, develop and drives the used setting and increase the reliability of elevator. The author also mentioned to achieve high speed nine-phase Permanent Magnet Synchronous Motor Control System.

In [10], the author mentioned that making of wireless module to realize the transmission of user information, PLC control system are adopted, the serial communication mode between the PLC and the wireless module was adopted. SI4432 Transceiver, Single-Chip computer and PLC are used to modify the control system of construction elevator. The control system of the construction elevator was made up of PLC, wireless calling device and wireless host transceiver. Elevator control system can determine the next travel direction based on the call information and the current operation automatically, realizes unattended operation.

In [11], the author described the application of sate chart to the modeling, design and implementation of an elevator system, whose system behavior involves aggregating complexity of state descriptions, and imposition of underlying control policy. Based on the operational flow of an elevator, they derive the associated state chart model by looking into the inherent hierarchical structure of the elevator. This research was supported in part by the grant NSC90-2213-E-011-020 and NSC90-2212-E-014-023 by the National Science Council, Taiwan, R.O.C.

PROGRAMMABLE LOGIC CONTROLLER

The first Programmable Logic Controller, PLC was developed by a group of engineers at General Motors in 1968. It was developed when that company was looking for an alternative to replace complex relay control system. The term ‘programmable logic controller’ is defined by EN 61131-1 as a digitally operating electronic system which uses a programmable memory for the internal storage of user-oriented instructions for implementing specific functions such as logic, sequencing, timing, counting and arithmetic to control through digital or analogue inputs and outputs, various machines or process.

A. Ladder Programming algorithm

There are many types of programming languages in Programmable Logic Controller, PLC. Languages are typically fixed to Ladder Logic (LD), Sequential Function Block (SFC), Function Block Diagram (FBD) and Structure Text (ST). The common program language of PLC is ladder diagram.

B. Ladder Logic

Ladder diagram is an automatic control diagram language that developed during World War II. Ladder logic is the primary programming language of programmable logic controllers. Since the PLC was developed to replace relay logic control systems, it was only natural that the initial language closely resembles the diagrams used to document the relay logic. By using this approach, the engineers and technicians using the early PLCs did not need retraining to understand the program. To introduce ladder logic programming simple switch circuits are converted to relay logic and then to PLC ladder logic. Any control task modifications are done by changing the program. This is why the use of the PLC is preferred to the traditional hard wired circuits in industrial controls.

 

Figure1. PLC Architecture

 

Figure2. Ladder diagram algorithm

In the chart of traditional ladder diagram, if X0, X1, X4 and X6 are in ON condition and the others are in OFF condition, output point Y0 will be in ON condition as shown as dotted line in the figure 2.

Implementation of PLC Based Elevator Control System

C. Ladder Software Package

The Auto Station installation package issued by Invt Auto-Control Technology is an executable program. The main interfaces include 7 sections: Menu, Tool bar, Project Manager Window, Instruction Tree window, Information window, Status bar and Operation area.

 

Figure3. Auto Station main interface

PROPOSED SYSTEM

In order to design a control circuit, it is divided into several units or modules for its particular task or control which first can be tested or implemented independently and then combined together. The basis of PLC based elevator control can be classified into three main groups. The first is the floor, the second is the PLC controller and the last is the Elevator. The block diagram of PLC Based Elevator Control System is described in Figure 4 to accomplish the PLC based control system, the design uses six major components: PLC controller, DC motor driver, push button, level sensor, display unit and Elevator. Level sensors are used to know the elevator position and push buttons are used to be input by the user request. The display unit will display the number of floor. The PLC compares the user request and the push button to drive the elevator motor Up or Down. When the user request is greater than the sensor value, the motor will go up and it is less than the sensor value, it will go down. When the two values are equal, the motor must stop.

 

Figure4. Block diagram of PLC based elevator control system

 Electrical and Electronics Project by Ravi Devani

This design can be divided into several units or modules. They are sensor unit, processing unit and power unit. There are some devices and components used in the in the design to implement each unit. These devices used in this system are as follows;

Ø Power Supply Unit

Ø Hall Effect sensor

Ø IVC1 1410MAT PLC controller

Ø H-bridge DC motor

Ø Push Button

Ø Display Unit

Ø Elevator

A. Power Supply Unit

The DC power supply unit is vital component in modern electronic devices as they need a wide range of DC voltages for their operations. The purpose of a power supply is to provide the required amount of power specified voltage from primary source.

B. Description of Hall Effect Sensor

A Hall Effect sensor is a transducer that varies its output voltage in response to a magnetic field. Hall Effect sensors are used for proximity, positioning, speed detection and current sensing applications. In its simplest form, the sensor operates as an analogue transducer, directly returning a voltage. A Hall Effect sensor can be used to measure the current without interrupting the circuit. Frequently, it is combined with circuitry that allows the device to act in a digital (on/off) mode and may be called a switch. It is commonly used to time the speed of wheels and shafts, such as for internal combustion engine ignition timing, tachometers and anti-lock braking systems. It consists basically of a thin piece of rectangular p-type semiconductor materials. A typical Hall Effect sensor has three wires or terminals; one for ground, one for supply or reference voltage and one for output. To produce an output signal, it must be supplied with a voltage from 5 to 12 V. There are many different types of magnet movements, such as Head-on, Sideways, Push-pull, and Push-push detections.

Implementation of PLC Based Elevator Control System

 

Figure5. (a) Heard on detection

 

(b) How Hall Effect works

C. Features of IVC1 1410MA TPLC Controller

The programmable controller PLC that is used in this research is IVC1 As shown in Figure 6, PORT0 and PORT1 are for communication. PORT0 is RS232, and use socket Mini DIN8, while PORT1 is RS485 or RS232. The bus socket is for connecting extension modules. The mode selector switch can be set to ON or OFF.

 

Figure6. Structure of IVCI series basic module

D. H-bridge DC Motor

Bidirectional control of a DC motor requires a circuit called an H-bridge, named for its schematic appearance, is able to move current in either direction through the motor winding. H-bridge topology was chosen in this system. An H-Bridge configuration using BJTs is shown in Fig 3.11. It is called an “H-bridge”, because it looks like an H letter. An H-bridge is an electronic circuit which enables electric motors to be run forward or backward action. It is mostly used in motor control of elevator. It is available as integrated circuits or can be built from separate components for specific design. In this system, the DC motor with H-bridge driver circuit advance the elevator car to the next position. The motor can provide for both directions: clockwise (CW) direction and counterclockwise (CCW) direction. This circuit uses four transistors for forward and reverse directions. Its operation is as follows. To rotate the DC motor four transistors are used. When the transistor Q1 and Q4 are ON and the other transistors are OFF, a positive voltage will be applied across the motor and the motor will rotate clockwise direction. When the transistor Q2 and Q3 are ON and the other transistors are OFF, the voltage across the motor will be negative, allowing counterclockwise operation of the motor. In DC motor, clockwise direction for Upcondition and counter clockwise direction is for Down-condition.

 

Figure7. H-bridge DC-motor Circuit

The motor used here is a H-bridge DC motor. Base on the design specification the output power and the output torque of the motor are calculated by a simple calculation. The power and torque calculation are mentioned as follow.

Weight of empty cabin = 100 kg

Counter weight = 100 kg

8persons with 65kg = 520 kg

For constant speed operation of 1m/s = 60m/1min

The power, work and force and torque are calculated using the equations (1 ), ( 2 ), (3 ), (4) and (5 ).

Power = work / time                   (1)

Work = Force x distance            (2)

Force, F = mg                             (3)

Power = Force x distance / time

So, Power = Force x velocity     (4)

F = 520 x 9.8 = 5096 N

P = 5096 x 1m/s = 5096 W

1hp = 745 W

5096 W = 6.84 hp (approximately 7hp or 5215W)

Rotational Speed _= 1500rpm

The torque of the motor can be calculated by using the equation(5)

Torque of motor (Nm) = 

                                                                     (5)

 Electrical and Electronics Project by Ravi Devani

SIMULATION RESULTS

The simulation of elevator position control is carried out with the Auto Station in order to know the performance of the controller. Auto Station software platform is use to perform the experiment. The PLC for experiment is equipped withIVC1-1410MAT programmable logic controller.

In this system, the ladder program must be run in the PLC controller by downloading ladder software.

Basic requirements are also needed;

Ø PLC

Ø Programming Device ( personal computer )

Ø Connector Cable

Ø Programming Software

A. Specification of PLC controller

IVC1 1410MAT programmable logic controller with Auto Station software has been chosen for developing and ladder logic was downloaded into the PLC. For the working model of an elevator various logics for different operations have to be developed and it is discussed in the following.

Table -1 SPECIFICATIONS OF IVC1 1410MAT DEVICE

 

B. Ladder logic for motor operation and to get signal from the floor sensors

The next step of receiving the input signal is to make the motor to operate either up or down direction and the logic has been developed correspondingly. Figure 8 shows the snap shot of the logic for the motor operation in both up and down direction. The motor operation is purely based on the input that the PLC gets from the push buttons. Based on the desired input and corresponding floor, the PLC wil make the motor to stop.

Outputs used for motor operation

1) Up motoring - O:4/1

2) Down motoring- O:4/1

 

Figure8. Ladder logic for motor Up and Down operation

C. Ladder logic for floor scan

As an initial move the ladder logic has to be developed for receiving the input signal from the push buttons and the same is used with the program to get the corresponding output based on this output.

Figure 9 describes the logic that has been developed to get the inputs from the call buttons present at every floor. When a particulars switch from the corresponding floor has been pressed the program in the PLC gets activated and the relevant bit will be activated.

Figure9. Ladder logic for scan floor

Implementation of PLC Based Elevator Control System

C. Ladder logic for close and move operation

The process of door closing has to start once the door has been fully opened so a sensor is placed at the end of door opening and when the sensor is cut a signal will be sent to the PLC. Figure 10illustrates the operation of door closing once the door opening operation comes to end that is when the sensor present at end for door opening has been cut. At the end of door closing the sensor will give a signal to the PLC will stop the door motor.

 

Figure10. Ladder logic for close and move operation

E. Ladder logic for tracking elevator car movement

Once the operation of the elevator motor ceases the logic has to be developed in such a way that it facilitates to track the elevator car movement. Based on the input from the floor sensors, the program downloaded in the PLC to track the movement. Figure 11 describes the operation of tracking movement. According to the input, the output O:2/12, O:2/13, O:2/14 and O:2/15 will be activated.

 

Figure11. Ladder logic for tracking movement operation

F. Ladder logic for stop and open door operation

The next step receiving the input signal is to stop the motor and then to open the door. After stopping the condition of motor, the door operation will activate at once. At the end of motor stopping the elevator car, the sensor will give a signal to the PLC. And then this will open the door motor. Figure12 express the operation of stop and open door according to the PLC controller.

 

Figure12. Ladder logic for stop and open door operation\

Figure13. GUI result of the complete fourth floors Elevator Control System

CONCLUSION

Although some calibrations and requirements may have, the modeling PLC based on elevator control system is done. The traditionally used relays and IC boards have been replaced by PLC for easy and cheap controlling of machines used in this elevator. By developing this proposed system, the result of elevator control system can be applied in the real world. By using PLC based elevator control system, the desired position can be forecasted. The simulation results of the four floors system have been discussed. As a future work, IVC1 1410MAT PLC based elevator model is intended to construct and tested to be applicable in the real world.

REFERENCE

[0] www.silicontechnolabs.in

[1] Yaing Sun, “Teaching Module Design of Elevator Controlled by PLC”, MICROCOMPUTER APPLICATIONS, 2013, pp.63-67, 31(5).

[2] Jie Zhang, “Application of PLC in elevator control system”, Journeel of Liaoning Normal University(Natural Science Edition), 2009, pp.318-320,32(3).

[3] Darshil, Sagar, Rajiv, Pangaokar and S.A. Sharma “Development of a PLC Based Elevator System with Colour Sensing Capabilities for

Material Handling in Industrial Plant”, Jiont International Conference on Power System Technology and IEEE Power India Conference, 2008,pp.1-7

[4]Jayawardana.H.P.A.P., Amarasekara.H.W.K.M., Peelikumura.P.T.S., Jayathilaka.W.A.K.C., Abeyaratne.S.G. and Dewasurendra.S.D. “Design and implenentation of astatechart based reconfigureurable elevator controller”, 6th IEEE International Industrial and Information Systems, IEEE Conference Publications, pp. 352-357

[5] Pillay, P., and Krishnan, Modeling of DC Motor Drives. IEEE Trans. Industry Applications, 1988, pp. 537-541, Vol. 35. no.4. IEEE database.

[6] Zhang Yajun, Chen Long, Fan Lingyan, “A Design of Elevator Positioning Control System Model,” IEEE Int. Conference Networks & Signal Processing, Zhenjiang, China, June 8-10. 2008, pp. 535-538.

[7] Hongqun Li, Yue Zhou, PLC Control and Real-time Monitoring of a Sightseeing Lift.Techniques of Automation & Applications, 2008,Vol.27 No.11.

[8] Xiaojuan Liu, Development of Elevator Monitor System Based on the Fieldbus, February 2008, Vol.30 No.1. Journal of EEE.

[9] S.B. Ron Carter, “Design and Implementation of PLC based Elevator”, April 2013, Volume 68_ No.7.

[10] Caiqiao Wei“Design of Control System of Construction Elevator Based on PLC”, 2014 4th Electronic System_ Integration Technology Conference.

[11] Yi-Sheng Huang, Sheng-Luen Chung, and Mu-Der Jeng “Modeling and Control of Elevator by State Chart”, June 2014, pp. 242-252,Asian Journal of Control, Vol. 6, No. 2.

 Electrical and Electronics Project by Ravi Devani